Join a book trader club and get books for free. All you do is mail the books you don't want to other people and order the books you want to read from the books listed on the websites.
Most people know that libraries are a great way to save money on books. Another way to save money is a book exchange with friends and family. An easy way to do this is to set up an email list with everyone that wants to participate and post the books you have available to share to the list. It can be fun social event and also saves you money. You can set up free email lists at the following places: